In a steam turbine, as a base material of parts and components making direct contact with steam, a 12% chromium stainless steel, for example, is used. In order to improve a resistance against erosion caused by solid particles existing in the steam, in the case of stationary parts and components, a surface of the base material often has applied thereto a boronizing treatment in which a penetration diffusion treatment of boron is carried out.
However, in the case of the above-mentioned 12% chromium stainless steel, there is a problem in that the parts and components are damaged by erosion due to solid particles included in the steam, such as silica, iron oxide or the like, so that their life becomes shorter. In order to solve such a problem, the surface of the 12% chromium stainless steel may have applied thereto the boronizing treatment, as mentioned above. Nevertheless, even in this case, a sufficient resistance against erosion due to solid particles is hardly obtained so that the fatigue strength is deteriorated. Thus, there is a problem that the above-mentioned surface treatment is hardly applied to rotating members.
Moreover, in the part making contact with a high temperature steam in a steam turbine or the like, not only the solid particle erosion resistance but also a sufficient performance including the oxidation resistance, fatigue strength and the like is demanded.
Conventionally, as a high speed rotator, such as a dynamic pressure fluid bearing or the like, there is disclosed, as in the Patent Document 1 below, a proposal that a base material has applied thereto a hardening treatment and is then coated with a diamond-like carbon membrane so as to cope with damage to the high speed rotator due to impurities, such as metal powders or the like, generated by abrasions and also to cope with deterioration of the rotating performance and life. Nevertheless, if an application to the part making contact with steam in a steam turbine is considered, practicability and applicability of such a surface treated coating are still insufficient not only with respect to the solid particle erosion resistance but also with respect to the oxidation resistance, fatigue strength or the like.    Patent Document 1: Japanese laid-open patent application 2002-188642 (page 1, FIG. 1)